Causes of non-gonococcal urethritis

Non-gonococcal urethritis (NGU) is most commonly caused by an infection, although there are many cases when no cause is found.

Although sexually transmitted infections (STIs) can cause NGU, it does not result from a gonorrhoea infection.


The STI chlamydia is thought responsible for almost half of all cases of NGU in men. In women, about 4 in 10 cases of NGU may be caused by chlamydia.

Chlamydia is caused by Chlamydia trachomatis bacteria and is spread during unprotected sex, including anal and oral sex.

Other infections

A number of other infections can cause NGU.

This includes other bacteria that usually live harmlessly in the throat, mouth or rectum. They can cause NGU if they manage to find their way into the urethra, which is the tube that carries urine from the bladder to the outside of the body. This can often occur during oral or anal sex.

Possible infections that can cause NGU include:

Non-infectious causes

It is possible for NGU to have a non-infectious cause. This is when something else leads to the urethra becoming inflamed. Non-infectious causes of NGU include:

  • irritation from a product used in the genital area, such as soap, deodorant or spermicide
  • damage to the urethra caused by vigorous sex or masturbation
  • damage to the urethra caused by inserting an object into it, such as a catheter (thin, plastic tube) which is inserted to allow urine to drain from the bladder, for example during an operation in hospital

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